Ultrasonic Anti-scaling and Descaling of Heat Exchanger

As general equipment in chemical, petroleum, power, food, and many other industrial sectors, heat exchangers have been plagued by the problem of scaling in the long-term industrial production process, which has always plagued the production and benefits of enterprises. At the end of the 20th century, Russia, South Korea, and other countries have taken the lead in adopting advanced ultrasonic anti-scaling technology.

 

The impact of fouling on heat exchanger is mainly reflected in two aspects. One is that the thermal conductivity of the fouling is very poor, which increases the thermal resistance of heat transfer and reduces the heat exchange efficiency of the heat exchanger. Second, when there is a fouling layer on the surface of the heat exchanger, the area of the fluid channel is reduced, which increases the resistance when the fluid flows through the equipment, thereby increasing pump power consumption and increasing the production cost of the enterprise.

 

Traditional cleaning methods include mechanical cleaning and chemical cleaning. No matter which method is used, the cost is very expensive. As far as the effect is concerned, it only treats the symptoms rather than the root cause, which not only affects production, but also has a series of problems such as wear and corrosion of equipment, pollution of the regional environment, and damage to the health of workers. Ultrasonic anti-scaling and descaling equipment, which is essentially different from traditional descaling methods, has been widely used for anti-scaling and descaling in heat exchangers and their pipelines because of its continuous online work, the high degree of automation, reliable performance, no environmental pollution, and low operating costs. 

 

The principle of ultrasonic descaling of heat exchanger

Ultrasonic descaling is a process of mechanical vibration propagating in the medium. The ultrasonic frequency is high and the wavelength is short. Ultrasonic descaling equipment is mainly composed of an ultrasonic generator, a sound transmission system, and a transducer in the heat exchanger pipeline. Ultrasonic anti-scaling mainly uses ultrasonic power and sound field to treat fluids, so that the scale substances in the fluid will change their physical and chemical indicators and morphology under the action of ultrasound, so that the scales are dispersed, loosened, crushed, and peeled off, and are not easy to adhere to the pipe wall. Achieve the effect of anti-scaling and descaling of the heat exchanger, and improve and increase the heat transfer efficiency. The principle of ultrasonic anti-scaling and descaling is mainly reflected in the following aspects:

1) Cavitation 

Ultrasonic energy directly produces a large number of cavities and bubbles on the fluid medium to be treated. When these cavities and bubbles burst and squeeze, a certain range of strong pressure peaks are generated, and the local pressure peaks can reach Thousands of atmospheres. Under the action of the pressure peak, the scale-forming substance is crushed and suspended in water, and the generated scale layer is broken to make it easy to fall off, to achieve the purpose of ultrasonic descaling.

 

2) Activation

Ultrasonic generates the "cavitation" effect in the fluid, improves the activity of flowing fluid and fouling substances, destroys the conditions for fouling generation and deposition on the heat exchanger tube wall, and disperses the fouling substances in the fluid. The deposit body does not form a hard scale on the pipe wall, to achieve the purpose of ultrasonic anti-scaling.

 

3) Shearing effect

Ultrasound radiates on the scale layer and the pipe wall and in the water. Due to the different frequency response to the ultrasonic, the three will produce asynchronous vibrations, thus producing high-speed relative motion. Due to the speed difference, the relative shearing force on the interface between the scale layer and the heat exchanger tube wall is formed, which causes the scale layer to fatigue and loosen, thus achieving the purpose of ultrasonic descaling.

 

4) Inhibition

Changing the physical and chemical properties of the fluid body through the action of ultrasound can inhibit the nucleation and growth of ions in the water on the wall. Therefore, the number of fouling ions adhering to the surface of the heat exchanger is reduced. Practical research has proved that the longer the ultrasonic action time, the better the effect of preventing fouling of fouling substances. In short, under the action of ultrasonic waves, when the ultrasonic energy is large enough, that is, "power ultrasound" can produce short, local, extremely high temperatures, high pressure, and high strength in the conductive medium under normal temperature and normal pressure. In the extreme physical environment of the electric field, the fluid will produce the so-called "acoustic cavitation effect", which will trigger many mechanical, physical, chemical, biological, and other effects to achieve the purpose of ultrasonic anti-scaling and descaling in the fluid.

 

Advantages of ultrasonic descaling of heat exchangers

1) After the use of ultrasonic anti-scaling and descaling, there is no need to do regular chemical descaling, because ultrasonic descaling and anti-scaling are carried out simultaneously. If there is a scale, it will descale, if there is no scale, it will prevent it. There are no worries for a long time.

 

2) The traditional work stoppage to clean up dirt is often an unplanned work stoppage. The partial shutdown of the device or equipment switching conditions will not only affect the normal production but also incur unplanned costs. The use of ultrasonic anti-scaling and descaling is completely online and does not conflict with production, making the production process more stable and reliable, and reducing unnecessary downtime.

 

3) The energy-saving effect is remarkable, with an average energy saving of 30%. And compared with other methods, the service life of the heat exchanger is prolonged, and the loss caused by the shutdown of descaling and production is avoided. The use of ultrasonic descaling saves costs for enterprises and creates economic benefits.

 

4) Ultrasonic anti-scaling and descaling is completely a physical process, without the use of any chemicals, no corrosion, no pollution, no harm to the health of the operator and the heat exchanger, and has good social benefits.

 

5) The use of ultrasonic anti-scaling and descaling has low power consumption and low operating cost. It can work continuously on-line and realize full automation without the need for specialized personnel to operate.

 

In short, the ultrasonic anti-scaling equipment has the dual function of not only preventing the formation of fouling but also destroying the existing fouling. The long-term practice has proved that this technology is the most effective and scientific method in modern descaling, and its promotion value has broad significance in environmental protection and energy-saving, improvement of work efficiency, and cost reduction.